Call Us: (973) 256-3000 Plast-O-Matic Valves, Inc.
1384 Pompton Avenue
Cedar Grove, NJ 07009 USA

Series GYW Wafer Style Double Wall Sight Flow Indicators

double wall sight glass in pvc, Corzan CPVC, PTFE, Kynar, or polypro

Advantages of Series GYW Sight Glasses:

  • Double-wall construction featuring Pyrex® inner wall
  • Large 360° viewing area.
  • Full flow design (no corners to collect debris).
  • Wide choice of select plastic materials to assure maximum chemical compatibility.
  • Little or no maintenance required.
  • No special hardware required for installation (completely assembled and pre-tested).

Design Features

True Blue® Series GYW flow indicators are designed to indicate the presence or clarity of high purity or corrosive liquid in a piping system. For use with ultrapure liquids or chemicals compatible with acrylic. O-ring seals are used on Series GYW indicators allowing them to seal at extremely low pressures as well as high pressures. GYW flow indicators are full ported, eliminating any possible flow resistance. Pipe sizes are 1-1/2" through 8" NPT (40 mm through 200 mm). An optional fluttering device is available.

Materials of Construction

Ends on Series "GYW" indicators are Geon® PVC, Corzan® CPVC, PTFE, Kynar® PVDF and Natural Polypropylene. Standard O-ring seals are Viton®. Standard fasteners are stainless steel. The transparent outer cylinder wall is high impact strength acrylic. The inner wall (wetted) is Pyrex (CAUTION: cannot be used with hydrofluoric acid or sodium hydroxide which will etch the glass). Optional fluttering devices are corrosion resistant thermoplastic.

Pressure & Temperature Charts

Series GYW with Geon® PVC Ends

double wall sight glass in pvc pressure and temperature chart

Series GYW with Polypropylene Ends

double wall sight glass in polypro pressure and temperature chart

Series GYW with Kynar® PVDF Ends (1-1/2 - 8" shown)

double wall sight glass in Kynar pressure and temperature chart

Series GYW with PTFE Ends

double wall sight glass in PTFE pressure and temperature chart


dimensional drawing of double wall wafer style sight glass
double wall sight glass table of dimensions Series GYW

Ordering Information

Pipe Size/InchesPipe Size/MillimetersPart # w/Polypropylene Ends

Natural Polypropylene ends are shown above. For Geon PVC, change -PP to -PV, for example: GYW150V-PV. For Corzan CPVC, change -PP to -CP. For Kynar PVDF, change -PP to -PF. For PTFE, change -PP to -TF. If a fulttering device is required, add -FD to the appropriate model number. If DIN installations are required, please specify "For DIN Assembly" on the order.

Operation & Use

When properly installed, Plast-O-Matic flow indicators are automatic in operation and require little or no attention.

These flow indicators will easily show the flow of turbulent liquids without assistance from fluttering devices. With clear or opaque liquids that are not turbulent and do not contain entrained air bubbles, the flow may be difficult to see. In this case a Plast-O-Matic fluttering device within the cylinder will indicate movement of the liquid.

Installation Considerations

All Plast-O-Matic flow indicators are easily installed in a piping system. The flow indicators may be installed either vertically or horizontally; however, the level indicators can only be installed vertically.

The Series "GYW" (wafer design) flow indicators simply slip between two smooth faced companion flanges that may be either metal or plastic. Flange gaskets are not required as these flow indicators are supplied with two O-rings for just that purpose. Care should be taken so there is no misalignment of the flanges. Flange bolts should be tightened gradually alternating between opposite bolts to insure that the assembly pulls together evenly. The final 1/16" of tightening should be done with a torque wrench set between 10 and 15 foot pounds. This will seal the O-rings without placing uneven or excessive stresses on the assembly.

Although these flow indicators have no specific inlet or outlet, care should be exercised when installing such units that have streamers for fluttering devices. They must be installed in such a manner that the fluid flow will force the streamers into the indicator's viewing area.

Cylinder Wall Information

Clearly, any flow or level indicator is only as good as the quality of its cylinder wall(s) since this is where the viewing takes place. The transparent cylinder walls used in PLAST-O-MATIC flow and level indicators are chosen for characteristics such as high corrosion resistance, high impact strength, and high light transmission.

The inner transparent cylinder walls used in the Series "GYW" are Pyrex, a borosilicate glass of very low alkali content that resists attack from most bases and acids with the exception of hydrofluoric acid and sodium hydroxide. This is the same material used in manufacturing glass pipe that is extensively used in the chemical, food, beverage and pharmaceutical industries.

The outer transparent cylinder walls are manufactured of a high impact strength acrylic. This material possesses uniform optical quality and has an extremely high light transmission factor, which is of great importance when the color or clarity of your liquid is a prime consideration. Acrylic cylinder walls are ultra-violet resistant.

Fluttering Devices

All PLAST-O-MATIC flow indicators can be used to indicate the presence of liquid flow when the liquid lends itself to turbulence or has entrained air bubbles that make viewing effortless. When the liquid is either clear or opaque a mechanical device is required to identify liquid movement. In such applications the use of PLAST-O-MATIC optional fluttering devices is a necessity. Optional devices that flutter in the presence of flow are available for Series GYW flow indicators.

Modified & Custom Sight Glasses

As specialists in thermoplastic sight glass design for over 30 years, Plast-O-Matic's engineering department can modify Series GYW...or create an all-new product for any special application. Depending on complexity, minimum quantities and/or design fees may apply. Please contact our Technical Sales Group at (973) 256-3000 for details.

Links to Web Pages with Specifications for each type of Sight Glass

Please click here for web page specific to Series GX Single cylinder wall flow indicators

Please click here for web page specific to Series GY Double-Wall Sight Glasses

Please click here for web page specific to Series GL Double Cylinder Wall, Pyrex & Acrylic Level Indicators

Please click here for the general page for all sight flow & level indicators offered by Plast-O-Matic Valves, Inc.

Links to PDF files

Please note that the above web pages are slightly more up-to-date than the .pdf files below, and the charts may print more clearly in the web pages. We suggest you try the above .html format, unless you need the convenience of "forwarding" .pdf files, etc. Thank you.

Please Click here for dimensional specifications, pressure & temperature ratings for all Sight Glasses & Level Indicators PDF format

Please click here for PDF file specific to Series GX Single cylinder wall flow indicators

Please click here for PDF file specific to Series GY Double cylinder wall flow indicators

Please click here for PDF file specific to Series GYW Double-Wall, Wafer Style Sight Glasses

Please click here for PDF file specific to Series GL Double Cylinder Wall, Pyrex & Acrylic Level Indicators

Plast-O-Matic Valves, Inc. 1384 Pompton Avenue Cedar Grove,
NJ 07009 USA Phone: (973) 256-3000 Fax: (973) 256-4745
California Warehouse 4054 Brewster Way Riverside, CA 92501
USA phone: (951) 686-2852 Fax: (951) 686-6328
Email: Legacy home page: please click here